[PDFBOX-4689] Invisible Signature should have empty Appearance Dictionary

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.17
• Fix Version/s: 2.0.18, 3.0.0 PDFBox
• Component/s: Signing
• Assignee: Tilman Hausherr
• Reporter: Stefan Strobl
• Created: 14/Nov/19 04:23
• Updated: 23/Dec/19 22:16
• Resolved: 01/Dec/19 13:50

Description

According to TechNote 0006: Digital Signatures in PDF/A-1
http://www.pdfa.org/wp-content/uploads/2011/08/tn0006_digital_signatures_in_pdfa-1_2008-03-141.pdf Section 2.4 "The visual appearance must also exist for an invisible signature but may be empty." 

This should be easily handled by modifying PDDocument as indicated below:

private void prepareNonVisibleSignature(PDSignatureField signatureField)
        throws IOException
{
    // "Signature fields that are not intended to be visible shall
    // have an annotation rectangle that has zero height and width."
    // Set rectangle for non-visual signature to rectangle array [ 0 0 0 0 ]
    signatureField.getWidgets().get(0).setRectangle(new PDRectangle());
+    signatureField.getWidgets().get(0).setAppearance(new PDAppearanceDictionary());
}

If this is an acceptable solution I would be happy to provide a PR

Issue Links

• relates to: PDFBOX-3114 Visible signatures in different pages changes previous revision
• links to: DSS-1815 - Upgrade PDFBox